The present invention relates to a liquid chromatographic apparatus and particularly to a liquid chromatographic apparatus having a flow cell suitable for a micro liquid chromatography.
A conventional liquid chromatographic apparatus uses a flow cell disclosed, for example, in Japanese Patent Application Laid-Open No.8-184551 as the detector. Quartz or stainless steel having a good chemical resistance is generally used for a cell body of the flow cell. A synthetic quartz is used for windows to transmit a detection light beam and the windows are optically bonded with the cell body when the cell body is made of quartz. The cell body made of quartz is composed of an inlet flow passage, an outlet flow passage and a detection flow passage for allowing the detection light beam to pass through, the detection flow passage being connected to the inlet flow passage and the outlet flow passage. A shape of these flow passages is Z-shaped to reflect an eluant passing through the inlet flow passage by being hit on the window so that the flow separation is suppressed.
In recent yeas, processing cost of liquid waste such as organic solvents has been increased due to growing environment problems. Accordingly, it is required to reduce a using amount (flow rate) of the eluant used in the liquid chromatographic apparatus. As the flow rate of the eluant is decreased, the flow passages of the column, the flow cell and the piping are required to be made small in size in order to make diffusion of a sample small. If the sample diffuses, a peak width of chromatogram is widened, and accordingly components in the sample having peaks close to each other cannot be separated and detected.
The size of the passages of the column and the piping can be made small. However, if the diameter of the detection flow passage is decreased, a light quantity of the detection light beam is decreased and the S/N ratio is degraded. Therefore, it is necessary to reduce the diffusion of sample without decreasing the diameter of the detection flow passage. However, there are the following three problems.
1. In a flow cell of conventional structure, when the inlet flow passage is thinned in order to reduce diffusion of a sample, the inlet flow passage is easily choked by precipitation particles of the eluant and the sample. There is a problem in that if the inlet flow passage is choked, the flow cell itself has to be exchanged.
2. In a case where the cell body of a flow cell is made of quartz, the flow passages such as the inlet flow passage and the detection flow passage are formed using an ultrasonic rotary working machine. However, in boring in a quartz member using the ultrasonic rotary working machine, the minimum manufacturable diameter of the working tool is 0.4 mm, and a finishing diameter of 0.5 mm is minimum. Therefore, there is a problem in that the diameter of the inlet flow passage cannot be made smaller than the value and diffusion of sample becomes large in a quartz flow cell.
3. In a case where the diameter of the detection flow passage is not thinned in the conventional Z-shaped passage, there is a problem in that flow stagnates to increase an amount of the sample remaining at a corner portion of the detection flow passage.